X87: [turbofan] Implemented the optional Float32RoundTruncate operator.

src/compiler/x87/instruction-selector-x87.cc

Index: src/compiler/x87/instruction-selector-x87.cc
diff --git a/src/compiler/x87/instruction-selector-x87.cc b/src/compiler/x87/instruction-selector-x87.cc
index ccd99581e4a8e9c3791f0dbaa0cf6d176cf14eef..e613726e6df6c09369c1b28e40258ddfc8c2264c 100644
--- a/src/compiler/x87/instruction-selector-x87.cc
+++ b/src/compiler/x87/instruction-selector-x87.cc
@@ -871,7 +871,9 @@ void InstructionSelector::VisitFloat64RoundUp(Node* node) {
 
 
 void InstructionSelector::VisitFloat32RoundTruncate(Node* node) {
-  UNREACHABLE();
+  X87OperandGenerator g(this);
+  Emit(kX87Float32Round | MiscField::encode(kRoundToZero),
+       g.UseFixed(node, stX_0), g.Use(node->InputAt(0)));
 }
 
 
@@ -1319,6 +1321,7 @@ InstructionSelector::SupportedMachineOperatorFlags() {
            MachineOperatorBuilder::kFloat64RoundDown |
            MachineOperatorBuilder::kFloat32RoundUp |
            MachineOperatorBuilder::kFloat64RoundUp |
+           MachineOperatorBuilder::kFloat32RoundTruncate |
            MachineOperatorBuilder::kFloat64RoundTruncate |
            MachineOperatorBuilder::kFloat64RoundTiesEven;
   return flags;